Cardiovascular physiologic control mechanisms will be studied in intact unanesthetized dogs instrumented for direct measurement and radiotelemetry of cardiac dimensions and pressure, myocardial contractility, coronary and regional blood flows and arterial pressure. Miniature pressure gauges will be implanted in the left ventricle and aorta, ultrasonic dimension transducers will be opposed on the epi or endocardial surfaces of the left ventricle and Doppler ultrasonic or electromagnetic flow probes will be placed on the coronary, mesenteric, renal and iliac arteries. Myocardial, coronary and regional circulatory control mechanisms will be examined in normal, healthy conscious dogs and dogs with induced cardiovascular lesions, such as hypertension, A-V shunts and heart failure. The first section of the proposal, dealing with physiological control in normal animals, will concentrate 1) on neural control by baroreceptors, chemoreceptors, cardiac receptors and lung inflation receptors in the presence and absence of deafferentation and selective autonomic blockades, and 2) on the effects of cardiovascular stress, e.g., severe exercise, excitement, hemorrhage and hypoxia. In the second major section of the proposal the effects of these physiological interventions will be assessed in conscious dogs as they gradually develop the induced cardiovascular lesions. Thus, the aim of this research proposal is to gain a clearer understanding of the control of the cardiovascular system in the normal conscious animal and apply this knowledge to delineate the pathogenesis and control of the cardiovascular system in the presence of circulatory impairment. BIBLIOGRAPHIC REFERENCES: McRitchie, R.J., and S.F. Vatner: The role of arterial baroreceptors in mediating the cardiovascular responses to a cardiac glycoside in conscious dogs. Circ. Res. 38: 321-326, 1976. McRitchie, R.J., S.F. Vatner, D.H. Boettchner, G.R. Heyndrickx, T.A. Patrick, and E. Braunwald: The role of arterial baroreceptors in mediating the cardiovascular response to exercise. Am. J. Physiol. 230: 85-89, 1976.